By KAREN KAPLAN, Los Angeles Times

Published 11:00 pm, Tuesday, November 15, 2011

LOS ANGELES -- Children with high IQs are more likely to use marijuana, cocaine, amphetamines and other illicit drugs as teenagers and adults, according to new data on nearly 8,000 British men and women who were tracked for more than three decades.

Researchers from Cardiff University and University College London became interested in the question after other studies found that kids who scored high on intelligence tests were more likely than their peers to become heavy drinkers and alcoholics when they grew up.

For the new study, James White and G. David Batty examined data from the 1970 British Cohort Study, which has tracked thousands of people who were born in the same week of April 1970. Many of these kids took IQ tests at age 5 and/or age 10. As part of the study, participants were asked about their drug use when they were 16 years old and again when they were 30.

Using that data, White and Batty divided the people into three groups based on their IQ scores (low, medium and high). They found that those in the top IQ group at age 5 were more likely than those in the bottom IQ group to have ever used marijuana by the time they were 16. At age 30, women with high IQ scores were more than twice as likely as low-IQ women to have used marijuana or cocaine in the prior year, while men with high IQs were 46 percent more likely to have used amphetamines and 65 percent more likely to have used ecstasy than their low-IQ counterparts.

When the researchers looked at IQ scores from age 10, the results were similar.

Overall, the link between high IQ and drug use was stronger for women than men. The statistical analysis controlled for certain other factors that could have influenced drug use, such as psychological stress and socioeconomic status.

The results may seem surprising at first glance, but the researchers noted that they do fit some established patterns. "High-IQ individuals have also been shown to score highly on tests of stimulation seeking and openness to experience," they wrote, and it could be that "illegal drugs are better at fulfilling a desire for novelty and stimulation."

Two other traits linked with childhood intelligence -- boredom and a tendency to be teased by one's peers -- could also fuel an interest in "using drugs as an avoidant coping strategy," the researchers added.

The study was published online Monday by the Journal of Epidemiology and Community Health.